1. Field of the Invention
The present invention relates to a check valve assembly especially adapted for use with a reciprocating pump, particularly for use with a very high pressure pump.
2. Description of the Prior Art
For use with a reciprocating pump, a common arrangement is to provide a valve assembly where there are two conventional check valves joined by a "T" connection. On the intake stroke of the pump, one of the check valves opens to permit liquid from a low pressure source to flow into the pump, and on the discharge stroke of the pump the other check valve opens to permit the outflow of the liquid under pumping pressure.
However, when very high pressures are involved, the "T" configuration of the valve housing is undesirable since stress concentrations occur which result in early fatigue failure. Hence, it has been undertaken to provide a valve assembly where the check valves are coaxially arranged so that the components of the valve assembly are cylindrically symmetrical. With such an arrangement, the stress concentrations inherent in the "T" configuration are relieved and the valve assembly is capable of operating under high fluctuating pressures without such premature fatigue failure.
In one such prior art configuration, there is an outlet check valve of a conventional type which comprises a spring loaded valve element that fits in a conical seat formed at the outlet opening in the valve housing. Also, there is an inlet check valve which has a valve element of an annular configuration which seats in an annular inlet opening at the opposite end of the housing. With this annular configuration of the valve element of the inlet valve, on the power stroke of the associated pump, the valve element permits high pressure liquid from the pump to flow through the center opening of the valve element and through an axially aligned passage in the valve housing to pass out through the outlet valve. On the intake stroke, low pressure liquid is taken in through the inlet passages symmetrically arranged in the valve housing to flow into the annular intake opening, with the annular valve element moving away from seating engagement to permit this inflow of low pressure liquid.
While such a valve arrangement does relieve the stress concentrations associated with the "T" configuration of a valve assembly, where very high pressures are involved (e.g. in the order of 50,000 psi or more), the valve elements themselves in moving between their open and closed positions are subjected to rather severe loads which create a tendency for these valve elements and the parts they contact to wear. In the particular configuration of a coaxial valve described above, the annular intake valve element and those portions of the housing with which it comes in contact as it seats in its closed position are especially susceptible to wear which ultimately impairs the ability of the valve element to function properly.
In view of the foregoing, it is an object of the present invention to provide a coaxial valve assembly, such as that described above, which alleviates some of the problems of premature wear experienced in prior art valve assemblies such as those described above.